The use of Raman spectroscopy as a versatile characterization tool for calcium sulphoaluminate cements: a compositional and hydration study

Calcium sulphoaluminate (CSA) cement is considered the third series cement besides ordinary Portland cement (OPC) and calcium aluminate (CA) cement. It is produced from gypsum, bauxite and limestone at 1,300 °C and consists of yeelimite, belite and anhydrite as main mineral phases. In the last years, many attempts have been made in applying Raman spectroscopy for the characterization of cement, clinker minerals and supplementary cementing materials (SCMs), revealing that this technique is a valuable tool for the identification of different phases in cements. In this work micro-Raman spectroscopy has been used, together with X-ray diffraction, for the characterization of CSA cement and its main minerals. In order to identify which mineral phase is responsible for the different bands, Raman spectra have been acquired from synthesized yeelimite and belite phases (whose purity degree was checked by X-ray diffraction) and from calcium sulphate di-hydrate and anhydrous (gypsum and anhydrite, respectively). On these bases, Raman spectra collected on CSA clinker and cement have been successfully assigned. Moreover, Raman spectroscopy, together with X-ray diffraction, proved useful to follow the hydration process of CSA cement up to 28 days.